The present invention relates generally to plasma etch processes, and more particularly, to methods and systems for controlling plasma etch processes.
Semiconductor device dimensions are pressed to ever smaller dimensions to enable more devices per wafer with higher performance. As semiconductor device dimensions become smaller, new challenges are presented in the process technology needed to form the smaller, more densely packed devices with high yield. These process requirements demand a precise control of plasma chemistry (radical, neutral and ions) to meet both on die as well as across semiconductor wafer etch requirements.
FIG. 1 is a side view of a simplified schematic drawing of a typical narrow gap plasma processing chamber 100. Process gases 102 are injected through a substantially central location 104 of the top portion 108 of the plasma processing chamber 100. The process gases 102 are injected into the plasma processing volume 110 defined as being over the semiconductor wafer 101 to be processed. The semiconductor wafer 101 is supported on a wafer support 106.
The process gases 102 flow in a substantially radial direction 112 through the plasma processing volume 110 toward a plasma confinement structure 114 at the periphery of the plasma processing volume. The process gases 102 and plasma process byproducts are pumped out at the periphery 114 through peripheral vents 116 to one or more vacuum pumps 118.
Typical plasma processes are performed at fixed process gas 102 pressure and flow. The fixed process gas 102 pressure and flow often causes radial pressure distributions. By way of example, the pressure P1, P2, P3 in each respective portion 120, 122, 124, 126 of the plasma processing volume 110 can vary due to convective flow and other causes.
What is needed is a system, method and apparatus for dynamically changing and controlling the peripheral conductance of the process gases so as to induce a fast change in the pressure in the plasma processing volume 110.